The compound that donates electrons (and therefore is oxidized). In bioremediation, the organic contaminant often serves as an electron donor.
Our approach to substrate dosing is based on site conditions. JRW Bioremediation L.L.C. provides substrates and nutrients for anaerobic bioremediation. The substrates provided include highly soluble materials such as WILCLEAR® sodium and potassium lactate, SoluLac® ethyl lactate, and Wilke Whey® whey powder and slowly soluble substrates including LactOil® soy micro-emulsion, and ChitoRem® chitin complex.
Carbon substrates for enhanced reductive dechlorination can be divided into two main categories related to their longevity in the subsurface: slowly soluble and readily soluble substrates. These categories can be better defined by the dissolution rate of the substrate with readily soluble substrates being materials that are miscible or semi-miscible in groundwater and slowly soluble substrates being generally recognized as dissolving over a period of multiple months. The dissolution rate is an important characteristic as it gives a clue to how much substrate is required per period.
Since the addition of a substrate is intended to establish and maintain conditions supportive of robust anaerobic metabolism for a period sufficient to completely degrade the contaminants, it is important to understand how much substrate will be available for metabolism over any given period. In general, because they dissolve more slowly, less soluble substrates require higher dosing to maintain the same amount of available dissolved carbon within a system per unit time. If the goals of the project require maintaining anaerobic conditions for an extended period, the design should allow for multiple injections and/or the use of a slowly soluble substrate. If the project goals require maintaining anaerobic conditions for only a short period of time (on the order of months rather than a year to two), the design can include a highly soluble substrate.
The physical properties of a substrate will also impact subsurface distribution. Post-injection distribution is impacted by advective flow and to some extent chemical diffusion. Highly substrates like WILCLEAR®, WILCLEAR Plus®, and SoluLac™ can mimic water in their movement in the subsurface and are ideal for re-circulation systems with limited injection points. They can also quickly diffuse in tight formations or formations with minimal groundwater flow.
WILCLEAR® sodium lactate and potassium lactate are both highly soluble substrates. Sodium lactate was one of the first substrates to be used in the field to enhance reductive dechlorination. Both are easy to use and store and are excellent substrates for recirculation systems.
Slowly soluble substrates like LactOil® soy microemulsion and ChitoRem® chitin complex can maintain anaerobic conditions in most aquifers for over two years.
LactOil® is unique in that the micro-emulsion allows the diluted material to have physical properties similar to highly soluble substrates while still retaining the slow dissolution properties of a vegetable oil. This combination provides the best characteristics of both highly soluble substrates (superior dispersion characteristics) and vegetable oils (longevity).
ChitoRem® chitin complex is a solid matrix that contains protein, chitin, and calcium carbonate. The protein provides an immediately available carbon source, the chitin provides a slow release carbon source and trace nitrogen for improved microbial growth, and the calcium carbonate provides a buffering agent. This material is ideal as an excavation or as a high-pressure fracturing substrate. ChitoRem® is also being developed as a bioreactor substrate for acid mine drainage (mine influenced water).
JRW provides information regarding our products as a service to our clients. JRW is not a consultant and does not provide professional services. Every site is unique and care must be exercised by the practitioner to fully understand their own circumstances
Enhanced reductive dechlorination is based on attaining and maintaining control of an aquifer for a period of time sufficient to degrade all constituents of concern and their daughter products. Attaining and maintaining control of an aquifer is highly dependent on the hydrogeology and geochemistry of the site along with the microbial populations present. Since the hydrogeology and geochemistry is different for every site, a blanket cost can not be given for any specific site. In general, enhanced reductive dechlorination will cost less than $10 per cubic yard of media treated on most non-DNAPL sites. This compares with about $60 per cubic yard for excavation (without disposal) and about $90 per cubic yard for chemical oxidation.
Because freight is costed from a warehouse to a delivery point, freight costs are quoted separately. Unless otherwise stated, due to the volatility of the fuels market, freight costs are generally valid for 30 days. Consideration should be given to the receiving facility’s capacity to off load a truck. In situations where the product is delivered to a facility without the capacity to off-load a delivery vehicle, arrangements can be made (for an additional charge) for delivery on a vehicle with a lift gate and pallet jack.
Reinjection schedules should be based on the geochemistry of an aquifer and not on a calendar schedule. In many cases, multiple injections can be spaced further apart over time.
Since the main goal of adding a substrate to an aquifer is to attain and maintain anaerobic conditions for an extended period of time, because of the limited flows clay sites should be ideal for enhanced reductive dechlorination. In practice, clay sites with adequately spaced injection points usually show very rapid response to substrate addition.
Injection spacing should be sufficient to promote robust reductive dechlorination throughout the treatment zone for a time sufficient to attain complete reductive dechlorination. Injection spacing is dependent upon the dissolution rate of the substrate, the dosage, aquifer velocity, and competing electron acceptor and contaminant flux.
